A wireless multihop network, a network in which a plurality of nodes are connected in a mesh shape, does not require a communication line and is excellent in maintainability. Therefore, a sensor network for monitoring a wide range and the like can be easily installed and maintained. A mechanism is known in which time division communication is applied to the wireless multihop network so as to cause the nodes to sleep in time zones unrelated to communication. The mechanism enables saving of energy resources (power saving).
In the wireless multihop network, since data is collected to a concentrator by relaying communication between nodes, it is necessary to determine a parent node to be a relay destination of data of each node. If there are a plurality of parent node candidates, it is necessary to select a parent node from among the parent node candidates. As a method for selecting a parent node, a scheme called ETX (Expected Transmission) is widely known. In the ETX scheme, a parent node with such a route that increases a communication success rate can be selected.
In the EXT scheme, however, there is a problem that congestion occurs due to concentration of data to a part of nodes on a route. When congestion occurs, it may be impossible to relay received data, or received data may be lost.